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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Chain width expansion
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On 10/15/19 8:50 AM, Joachim Str=C3=B6mbergson wrote:
>>>>> [...] to generate much longer chain with superslow timestamp increa=
se (~5 blocks in 1 second) without increasing difficulty (i.e. staying at=
min. diff.). [...]
>>>>> In that case, it would take about 7 minutes of block time seconds f=
or
>>>>> the next retarget period, every 2016 blocks, and the difficulty wou=
ld
>>>>> adjust. The difficulty would adjust in that case as if 2 weeks of b=
locks
>>>>> had been mined in 7 minutes. For the difficulty to remain the same =
the
>>>>> time between blocks needs to be 10 minutes.
>>>>> This calculation does not apply under time warp attack. You can fak=
e timestamps of all blocks except for those relevant to the retarget calc=
ulation. Those are only the first and the last block in the 2016 block wi=
ndow.
>> This must be in reference to the non-overlapping difficulty calculatio=
n
>> and off-by-one bug?
> Indeed.
>
Yeah, limiting the width of the chain would not be effective unless the
timewarp off-by-one bug is resolved =E2=80=94 the height can be extended =
instead.
Rate limiting based on chainwork would slow down a timewarped low work
header chain. There would be a maximum rate at which the headers could
be sent. It would be around 32KB/s. It would take about a month to send
100GB.
|
